1. Field of the Invention
This invention relates generally to long distance carriers, Internet Service Providers (ISPs), and information content delivery services/providers and long distance carriers. More particularly, it relates to emergency call systems (e.g., E9-1-1) including wireless and Internet Protocol (IP) based Voice Over Internet Protocol (VoIP) emergency call systems.
2. Background of Related Art
9-1-1 is a phone number widely recognized in North America as an emergency phone number that is used to contact emergency dispatch personnel. Enhanced 9-1-1 (E9-1-1) is defined by an emergency call being selectively routed to an appropriate PSAP, and enhanced information (callback number, name and location) is provided to the PSAP. This is accomplished through the use of the ANI. The ANI may be the real phone number of the caller (in landline E911) or a pseudo-ANI called an ESRK (in cellular E911) or ESQK (in VoIP E911). Regardless of the network type, a 9-1-1 service becomes E-9-1-1 when automatic number identification and automatic location information related to the call is provided to the 9-1-1 operator at the PSAP.
This identifier allows the PSAP to retrieve location information such as the Master Street Address Guide (MSAG) valid address of the E9-1-1 caller's Civic/Postal Address. The Master Street Address Guide (MSAG) represents a community provided local address master guide that permits the most accurate dispatch of emergency personnel to a “correct address.” The “correct address” originates as the civic/postal address of an E9-1-1 emergency caller over a wireless and/or Internet Protocol (IP) based Voice Over Internet Protocol (VoIP) emergency call system. The civic/postal address represents the caller's location at the time when the emergency call is placed. This civic/postal address needs to be associated with an appropriate corresponding MSAG address, which in most cases is required by the public safety answering point (PSAP).
A Public Service Answering Point (PSAP) is a dispatch office that receives 9-1-1 calls from the public. A PSAP may be a local, fire or police department, an ambulance service or a regional office covering all services. As used herein, the term “PSAP” refers to either a public safety access point (PSAP), or to an Emergency Call Center (ECC), a VoIP term.
Distributed emergency call systems in telecommunications are in general very complex computing systems. Emergency calls that originate from a VoIP network use well proven routing paradigms already used for cellular 911 calls, or for traditional landline 911 calls. These paradigms usually work well, because VoIP customers can usually be grouped into two categories: a mobile VoIP caller that resembles a cellular user, and a stationary VoIP user resembling landline usage.
Traditional landline systems use pre-provisioned, generally static subscriber addresses, where the landline automatic location identification (ALI) provisioning process insures a match to a master street address guide (MSAG) record, which contains an emergency service number (ESN) used to route emergency calls to a PSAP.
But determination of the location of a mobile device proves much, much more challenging. To determine location of a mobile device, some conventional cellular systems use separate triangulation technologies (or any of a number of other techniques) to find a latitude & longitude of an emergency caller. These systems then use a geographic information system (GIS) system to query for a pre-defined region (e.g., a PSAP polygon) that contains this location.
Of course, errors may occur in conventional systems when determining the location of a mobile user. But even though it's very possible that these queried PSAP polygons can lead to a different (i.e., wrong) neighboring PSAP than an equivalent address provisioned in a landline ALI, this discrepancy is conventionally accepted by PSAPs because the location itself is likely to be imprecise due to measurement errors—sometimes the location is off by hundreds of feet.
Conventional VoIP systems use proprietary technologies, usually based on GIS polygons, or based on pre-provisioning of the caller in the traditional landline ALI long before the need for an emergency call.
Thus, traditional landline paradigms provide the most accurate location for its static users, but require the caller's address to be pre-provisioned into a landline automatic location identifier (ALI). This pre-provisioning (often referred to as service order interface (SOI) loading) usually takes a few days between the caller notifying their service provider of their address change, and this change being reflected in the landline ALI. But during this window a 911 call might be made, and if so it would be routed using the “old” data still in the landline ALI. Even the fastest possible conventional landline ALI provisioning takes at least several hours.
Existing solutions include the NENA VoIP architecture for enhanced 9-1-1 services standard NENA 08-001. However, such conventional technologies are too complicated and not always practical. Moreover, conventional systems are disadvantageous because they are unable to handle the embedded geographic location to precisely route the caller to the correct PSAP using the “just-in-time” paradigm.
A “simple match” to find an MSAG-valid address refers to a simple lexicographic comparison of an input civic/postal address against the entries in an MSAG address store to find a positive match. The present inventors have appreciated that house numbers prove to be particularly hard to compare as in many cases house numbers contain digits and alpha-numeric characters in any random order. Given this fact, two house numbers that are not character-for-character identical may refer to the same house number as determined by a human observer.
Compounding this issue is the fact that otherwise conventional MSAG data stored in an otherwise conventional MSAG address data store is always given as range data including a low and high house number, e.g., “100-2000 Elm Street.” So with this, a simple match must successfully determine if a given input civic/postal house number falls within a stored MSAG address house number range.
The MSAG-valid address is required by most PSAPs, as it represents a community provided local address that allows accurate dispatch of emergency personnel to the correct address. But a challenge remains to provide a MSAG-valid address, particularly with respect to a real-time Voice Over Internet Protocol (VoIP) emergency call.